1 /* trees.c -- output deflated data using Huffman coding
2
3 Copyright (C) 1997-1999, 2009-2023 Free Software Foundation, Inc.
4 Copyright (C) 1992-1993 Jean-loup Gailly
5
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
9 any later version.
10
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software Foundation,
18 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
19
20 /*
21 * PURPOSE
22 *
23 * Encode various sets of source values using variable-length
24 * binary code trees.
25 *
26 * DISCUSSION
27 *
28 * The PKZIP "deflation" process uses several Huffman trees. The more
29 * common source values are represented by shorter bit sequences.
30 *
31 * Each code tree is stored in the ZIP file in a compressed form
32 * which is itself a Huffman encoding of the lengths of
33 * all the code strings (in ascending order by source values).
34 * The actual code strings are reconstructed from the lengths in
35 * the UNZIP process, as described in the "application note"
36 * (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program.
37 *
38 * REFERENCES
39 *
40 * Lynch, Thomas J.
41 * Data Compression: Techniques and Applications, pp. 53-55.
42 * Lifetime Learning Publications, 1985. ISBN 0-534-03418-7.
43 *
44 * Storer, James A.
45 * Data Compression: Methods and Theory, pp. 49-50.
46 * Computer Science Press, 1988. ISBN 0-7167-8156-5.
47 *
48 * Sedgewick, R.
49 * Algorithms, p290.
50 * Addison-Wesley, 1983. ISBN 0-201-06672-6.
51 *
52 * INTERFACE
53 *
54 * void ct_init (ush *attr, int *methodp)
55 * Allocate the match buffer, initialize the various tables and save
56 * the location of the internal file attribute (ascii/binary) and
57 * method (DEFLATE/STORE)
58 *
59 * void ct_tally (int dist, int lc);
60 * Save the match info and tally the frequency counts.
61 *
62 * off_t flush_block (char *buf, ulg stored_len, int eof)
63 * Determine the best encoding for the current block: dynamic trees,
64 * static trees or store, and output the encoded block to the zip
65 * file. Returns the total compressed length for the file so far.
66 *
67 */
68
69 #include <config.h>
70 #include <ctype.h>
71
72 #include "tailor.h"
73 #include "gzip.h"
74
75 /* ===========================================================================
76 * Constants
77 */
78
79 #define MAX_BITS 15
80 /* All codes must not exceed MAX_BITS bits */
81
82 #define MAX_BL_BITS 7
83 /* Bit length codes must not exceed MAX_BL_BITS bits */
84
85 #define LENGTH_CODES 29
86 /* number of length codes, not counting the special END_BLOCK code */
87
88 #define LITERALS 256
89 /* number of literal bytes 0..255 */
90
91 #define END_BLOCK 256
92 /* end of block literal code */
93
94 #define L_CODES (LITERALS+1+LENGTH_CODES)
95 /* number of Literal or Length codes, including the END_BLOCK code */
96
97 #define D_CODES 30
98 /* number of distance codes */
99
100 #define BL_CODES 19
101 /* number of codes used to transfer the bit lengths */
102
103
104 static int near extra_lbits[LENGTH_CODES] /* extra bits for each length code */
105 = {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0};
106
107 static int near extra_dbits[D_CODES] /* extra bits for each distance code */
108 = {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};
109
110 static int near extra_blbits[BL_CODES]/* extra bits for each bit length code */
111 = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};
112
113 #define STORED_BLOCK 0
114 #define STATIC_TREES 1
115 #define DYN_TREES 2
116 /* The three kinds of block type */
117
118 #ifndef LIT_BUFSIZE
119 # ifdef SMALL_MEM
120 # define LIT_BUFSIZE 0x2000
121 # else
122 # ifdef MEDIUM_MEM
123 # define LIT_BUFSIZE 0x4000
124 # else
125 # define LIT_BUFSIZE 0x8000
126 # endif
127 # endif
128 #endif
129 #ifndef DIST_BUFSIZE
130 # define DIST_BUFSIZE LIT_BUFSIZE
131 #endif
132 /* Sizes of match buffers for literals/lengths and distances. There are
133 * 4 reasons for limiting LIT_BUFSIZE to 64K:
134 * - frequencies can be kept in 16 bit counters
135 * - if compression is not successful for the first block, all input data is
136 * still in the window so we can still emit a stored block even when input
137 * comes from standard input. (This can also be done for all blocks if
138 * LIT_BUFSIZE is not greater than 32K.)
139 * - if compression is not successful for a file smaller than 64K, we can
140 * even emit a stored file instead of a stored block (saving 5 bytes).
141 * - creating new Huffman trees less frequently may not provide fast
142 * adaptation to changes in the input data statistics. (Take for
143 * example a binary file with poorly compressible code followed by
144 * a highly compressible string table.) Smaller buffer sizes give
145 * fast adaptation but have of course the overhead of transmitting trees
146 * more frequently.
147 * - I can't count above 4
148 * The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save
149 * memory at the expense of compression). Some optimizations would be possible
150 * if we rely on DIST_BUFSIZE == LIT_BUFSIZE.
151 */
152 #if LIT_BUFSIZE > INBUFSIZ
153 error cannot overlay l_buf and inbuf
154 #endif
155
156 #define REP_3_6 16
157 /* repeat previous bit length 3-6 times (2 bits of repeat count) */
158
159 #define REPZ_3_10 17
160 /* repeat a zero length 3-10 times (3 bits of repeat count) */
161
162 #define REPZ_11_138 18
163 /* repeat a zero length 11-138 times (7 bits of repeat count) */
164
165 /* ===========================================================================
166 * Local data
167 */
168
169 /* Data structure describing a single value and its code string. */
170 typedef struct ct_data {
171 union {
172 ush freq; /* frequency count */
173 ush code; /* bit string */
174 } fc;
175 union {
176 ush dad; /* father node in Huffman tree */
177 ush len; /* length of bit string */
178 } dl;
179 } ct_data;
180
181 #define Freq fc.freq
182 #define Code fc.code
183 #define Dad dl.dad
184 #define Len dl.len
185
186 #define HEAP_SIZE (2*L_CODES+1)
187 /* maximum heap size */
188
189 static ct_data near dyn_ltree[HEAP_SIZE]; /* literal and length tree */
190 static ct_data near dyn_dtree[2*D_CODES+1]; /* distance tree */
191
192 static ct_data near static_ltree[L_CODES+2];
193 /* The static literal tree. Since the bit lengths are imposed, there is no
194 * need for the L_CODES extra codes used during heap construction. However
195 * The codes 286 and 287 are needed to build a canonical tree (see ct_init
196 * below).
197 */
198
199 static ct_data near static_dtree[D_CODES];
200 /* The static distance tree. (Actually a trivial tree since all codes use
201 * 5 bits.)
202 */
203
204 static ct_data near bl_tree[2*BL_CODES+1];
205 /* Huffman tree for the bit lengths */
206
207 typedef struct tree_desc {
208 ct_data near *dyn_tree; /* the dynamic tree */
209 ct_data near *static_tree; /* corresponding static tree or NULL */
210 int near *extra_bits; /* extra bits for each code or NULL */
211 int extra_base; /* base index for extra_bits */
212 int elems; /* max number of elements in the tree */
213 int max_length; /* max bit length for the codes */
214 int max_code; /* largest code with non zero frequency */
215 } tree_desc;
216
217 static tree_desc near l_desc =
218 {dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0};
219
220 static tree_desc near d_desc =
221 {dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0};
222
223 static tree_desc near bl_desc =
224 {bl_tree, (ct_data near *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0};
225
226
227 static ush near bl_count[MAX_BITS+1];
228 /* number of codes at each bit length for an optimal tree */
229
230 static uch near bl_order[BL_CODES]
231 = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};
232 /* The lengths of the bit length codes are sent in order of decreasing
233 * probability, to avoid transmitting the lengths for unused bit length codes.
234 */
235
236 static int near heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
237 static int heap_len; /* number of elements in the heap */
238 static int heap_max; /* element of largest frequency */
239 /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
240 * The same heap array is used to build all trees.
241 */
242
243 static uch near depth[2*L_CODES+1];
244 /* Depth of each subtree used as tie breaker for trees of equal frequency */
245
246 static uch length_code[MAX_MATCH-MIN_MATCH+1];
247 /* length code for each normalized match length (0 == MIN_MATCH) */
248
249 static uch dist_code[512];
250 /* distance codes. The first 256 values correspond to the distances
251 * 3 .. 258, the last 256 values correspond to the top 8 bits of
252 * the 15 bit distances.
253 */
254
255 static int near base_length[LENGTH_CODES];
256 /* First normalized length for each code (0 = MIN_MATCH) */
257
258 static int near base_dist[D_CODES];
259 /* First normalized distance for each code (0 = distance of 1) */
260
261 #define l_buf inbuf
262 /* DECLARE(uch, l_buf, LIT_BUFSIZE); buffer for literals or lengths */
263
264 /* DECLARE(ush, d_buf, DIST_BUFSIZE); buffer for distances */
265
266 static uch near flag_buf[(LIT_BUFSIZE/8)];
267 /* flag_buf is a bit array distinguishing literals from lengths in
268 * l_buf, thus indicating the presence or absence of a distance.
269 */
270
271 static unsigned last_lit; /* running index in l_buf */
272 static unsigned last_dist; /* running index in d_buf */
273 static unsigned last_flags; /* running index in flag_buf */
274 static uch flags; /* current flags not yet saved in flag_buf */
275 static uch flag_bit; /* current bit used in flags */
276 /* bits are filled in flags starting at bit 0 (least significant).
277 * Note: these flags are overkill in the current code since we don't
278 * take advantage of DIST_BUFSIZE == LIT_BUFSIZE.
279 */
280
281 static ulg opt_len; /* bit length of current block with optimal trees */
282 static ulg static_len; /* bit length of current block with static trees */
283
284 static off_t compressed_len; /* total bit length of compressed file */
285
286 static off_t input_len; /* total byte length of input file */
287 /* input_len is for debugging only since we can get it by other means. */
288
289 static ush *file_type; /* pointer to UNKNOWN, BINARY or ASCII */
290 static int *file_method; /* pointer to DEFLATE or STORE */
291
292 #ifdef DEBUG
293 extern off_t bits_sent; /* bit length of the compressed data */
294 #endif
295
296 extern long block_start; /* window offset of current block */
297 extern unsigned near strstart; /* window offset of current string */
298
299 /* ===========================================================================
300 * Local (static) routines in this file.
301 */
302
303 static void init_block (void);
304 static void pqdownheap (ct_data near *tree, int k);
305 static void gen_bitlen (tree_desc near *desc);
306 static void gen_codes (ct_data near *tree, int max_code);
307 static void build_tree (tree_desc near *desc);
308 static void scan_tree (ct_data near *tree, int max_code);
309 static void send_tree (ct_data near *tree, int max_code);
310 static int build_bl_tree (void);
311 static void send_all_trees (int lcodes, int dcodes, int blcodes);
312 static void compress_block (ct_data near *ltree, ct_data near *dtree);
313 static void set_file_type (void);
314
315
316 #ifndef DEBUG
317 # define send_code(c, tree) send_bits(tree[c].Code, tree[c].Len)
318 /* Send a code of the given tree. c and tree must not have side effects */
319
320 #else /* DEBUG */
321 # define send_code(c, tree) \
322 { if (verbose > 1) fprintf (stderr, "\ncd %3u ", (c) + 0u); \
323 send_bits(tree[c].Code, tree[c].Len); }
324 #endif
325
326 #define d_code(dist) \
327 ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
328 /* Mapping from a distance to a distance code. dist is the distance - 1 and
329 * must not have side effects. dist_code[256] and dist_code[257] are never
330 * used.
331 */
332
333 #define MAX(a,b) (a >= b ? a : b)
334 /* the arguments must not have side effects */
335
336 /* ===========================================================================
337 * Allocate the match buffer, initialize the various tables and save the
338 * location of the internal file attribute (ascii/binary) and method
339 * (DEFLATE/STORE).
340 * ATTR points to internal file attribute.
341 * METHODP points to the compression method.
342 */
343 void
344 ct_init (ush *attr, int *methodp)
345 {
346 int n; /* iterates over tree elements */
347 int bits; /* bit counter */
348 int length; /* length value */
349 int code; /* code value */
350 int dist; /* distance index */
351
352 file_type = attr;
353 file_method = methodp;
354 compressed_len = input_len = 0L;
355
356 if (static_dtree[0].Len != 0) return; /* ct_init already called */
357
358 /* Initialize the mapping length (0..255) -> length code (0..28) */
359 length = 0;
360 for (code = 0; code < LENGTH_CODES-1; code++) {
361 base_length[code] = length;
362 for (n = 0; n < (1<<extra_lbits[code]); n++) {
363 length_code[length++] = (uch)code;
364 }
365 }
366 Assert (length == 256, "ct_init: length != 256");
367 /* Note that the length 255 (match length 258) can be represented
368 * in two different ways: code 284 + 5 bits or code 285, so we
369 * overwrite length_code[255] to use the best encoding:
370 */
371 length_code[length-1] = (uch)code;
372
373 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
374 dist = 0;
375 for (code = 0 ; code < 16; code++) {
376 base_dist[code] = dist;
377 for (n = 0; n < (1<<extra_dbits[code]); n++) {
378 dist_code[dist++] = (uch)code;
379 }
380 }
381 Assert (dist == 256, "ct_init: dist != 256");
382 dist >>= 7; /* from now on, all distances are divided by 128 */
383 for ( ; code < D_CODES; code++) {
384 base_dist[code] = dist << 7;
385 for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {
386 dist_code[256 + dist++] = (uch)code;
387 }
388 }
389 Assert (dist == 256, "ct_init: 256+dist != 512");
390
391 /* Construct the codes of the static literal tree */
392 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
393 n = 0;
394 while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;
395 while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;
396 while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;
397 while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;
398 /* Codes 286 and 287 do not exist, but we must include them in the
399 * tree construction to get a canonical Huffman tree (longest code
400 * all ones)
401 */
402 gen_codes((ct_data near *)static_ltree, L_CODES+1);
403
404 /* The static distance tree is trivial: */
405 for (n = 0; n < D_CODES; n++) {
406 static_dtree[n].Len = 5;
407 static_dtree[n].Code = bi_reverse(n, 5);
408 }
409
410 /* Initialize the first block of the first file: */
411 init_block();
412 }
413
414 /* ===========================================================================
415 * Initialize a new block.
416 */
417 static void
418 init_block ()
419 {
420 int n; /* iterates over tree elements */
421
422 /* Initialize the trees. */
423 for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0;
424 for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0;
425 for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0;
426
427 dyn_ltree[END_BLOCK].Freq = 1;
428 opt_len = static_len = 0L;
429 last_lit = last_dist = last_flags = 0;
430 flags = 0; flag_bit = 1;
431 }
432
433 #define SMALLEST 1
434 /* Index within the heap array of least frequent node in the Huffman tree */
435
436
437 /* ===========================================================================
438 * Remove the smallest element from the heap and recreate the heap with
439 * one less element. Updates heap and heap_len.
440 */
441 #define pqremove(tree, top) \
442 {\
443 top = heap[SMALLEST]; \
444 heap[SMALLEST] = heap[heap_len--]; \
445 pqdownheap(tree, SMALLEST); \
446 }
447
448 /* ===========================================================================
449 * Compares to subtrees, using the tree depth as tie breaker when
450 * the subtrees have equal frequency. This minimizes the worst case length.
451 */
452 #define smaller(tree, n, m) \
453 (tree[n].Freq < tree[m].Freq || \
454 (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))
455
456 /* ===========================================================================
457 * Restore the heap property by moving down the tree starting at node k,
458 * exchanging a node with the smallest of its two sons if necessary, stopping
459 * when the heap property is re-established (each father smaller than its
460 * two sons).
461 * TREE is the tree to restore.
462 * K is the node to move down.
463 */
464 static void
465 pqdownheap (ct_data near *tree, int k)
466 {
467 int v = heap[k];
468 int j = k << 1; /* left son of k */
469 while (j <= heap_len) {
470 /* Set j to the smallest of the two sons: */
471 if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++;
472
473 /* Exit if v is smaller than both sons */
474 if (smaller(tree, v, heap[j])) break;
475
476 /* Exchange v with the smallest son */
477 heap[k] = heap[j]; k = j;
478
479 /* And continue down the tree, setting j to the left son of k */
480 j <<= 1;
481 }
482 heap[k] = v;
483 }
484
485 /* ===========================================================================
486 * Compute the optimal bit lengths for a tree and update the total bit length
487 * for the current block.
488 * IN assertion: the fields freq and dad are set, heap[heap_max] and
489 * above are the tree nodes sorted by increasing frequency.
490 * OUT assertions: the field len is set to the optimal bit length, the
491 * array bl_count contains the frequencies for each bit length.
492 * The length opt_len is updated; static_len is also updated if stree is
493 * not null.
494 * DESC is the tree descriptor.
495 */
496 static void
497 gen_bitlen (tree_desc near *desc)
498 {
499 ct_data near *tree = desc->dyn_tree;
500 int near *extra = desc->extra_bits;
501 int base = desc->extra_base;
502 int max_code = desc->max_code;
503 int max_length = desc->max_length;
504 ct_data near *stree = desc->static_tree;
505 int h; /* heap index */
506 int n, m; /* iterate over the tree elements */
507 int bits; /* bit length */
508 int xbits; /* extra bits */
509 ush f; /* frequency */
510 int overflow = 0; /* number of elements with bit length too large */
511
512 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
513
514 /* In a first pass, compute the optimal bit lengths (which may
515 * overflow in the case of the bit length tree).
516 */
517 tree[heap[heap_max]].Len = 0; /* root of the heap */
518
519 for (h = heap_max+1; h < HEAP_SIZE; h++) {
520 n = heap[h];
521 bits = tree[tree[n].Dad].Len + 1;
522 if (bits > max_length) bits = max_length, overflow++;
523 tree[n].Len = (ush)bits;
524 /* We overwrite tree[n].Dad which is no longer needed */
525
526 if (n > max_code) continue; /* not a leaf node */
527
528 bl_count[bits]++;
529 xbits = 0;
530 if (n >= base) xbits = extra[n-base];
531 f = tree[n].Freq;
532 opt_len += (ulg)f * (bits + xbits);
533 if (stree) static_len += (ulg)f * (stree[n].Len + xbits);
534 }
535 if (overflow == 0) return;
536
537 Trace((stderr,"\nbit length overflow\n"));
538 /* This happens for example on obj2 and pic of the Calgary corpus */
539
540 /* Find the first bit length which could increase: */
541 do {
542 bits = max_length-1;
543 while (bl_count[bits] == 0) bits--;
544 bl_count[bits]--; /* move one leaf down the tree */
545 bl_count[bits+1] += 2; /* move one overflow item as its brother */
546 bl_count[max_length]--;
547 /* The brother of the overflow item also moves one step up,
548 * but this does not affect bl_count[max_length]
549 */
550 overflow -= 2;
551 } while (overflow > 0);
552
553 /* Now recompute all bit lengths, scanning in increasing frequency.
554 * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
555 * lengths instead of fixing only the wrong ones. This idea is taken
556 * from 'ar' written by Haruhiko Okumura.)
557 */
558 for (bits = max_length; bits != 0; bits--) {
559 n = bl_count[bits];
560 while (n != 0) {
561 m = heap[--h];
562 if (m > max_code) continue;
563 if (tree[m].Len != (unsigned) bits) {
564 Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));
565 opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq;
566 tree[m].Len = (ush)bits;
567 }
568 n--;
569 }
570 }
571 }
572
573 /* ===========================================================================
574 * Generate the codes for a given tree and bit counts (which need not be
575 * optimal).
576 * IN assertion: the array bl_count contains the bit length statistics for
577 * the given tree and the field len is set for all tree elements.
578 * OUT assertion: the field code is set for all tree elements of non
579 * zero code length.
580 * TREE is the tree to decorate.
581 * MAX_CODE is the largest code with non zero frequency.
582 */
583 static void
584 gen_codes (ct_data near *tree, int max_code)
585 {
586 ush next_code[MAX_BITS+1]; /* next code value for each bit length */
587 ush code = 0; /* running code value */
588 int bits; /* bit index */
589 int n; /* code index */
590
591 /* The distribution counts are first used to generate the code values
592 * without bit reversal.
593 */
594 for (bits = 1; bits <= MAX_BITS; bits++) {
595 next_code[bits] = code = (code + bl_count[bits-1]) << 1;
596 }
597 /* Check that the bit counts in bl_count are consistent. The last code
598 * must be all ones.
599 */
600 Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
601 "inconsistent bit counts");
602 Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
603
604 for (n = 0; n <= max_code; n++) {
605 int len = tree[n].Len;
606 if (len == 0) continue;
607 /* Now reverse the bits */
608 tree[n].Code = bi_reverse(next_code[len]++, len);
609
610 Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
611 n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1u));
612 }
613 }
614
615 /* ===========================================================================
616 * Construct one Huffman tree and assigns the code bit strings and lengths.
617 * Update the total bit length for the current block.
618 * IN assertion: the field freq is set for all tree elements.
619 * OUT assertions: the fields len and code are set to the optimal bit length
620 * and corresponding code. The length opt_len is updated; static_len is
621 * also updated if stree is not null. The field max_code is set.
622 * DESC is the tree descriptor.
623 */
624 static void
625 build_tree(tree_desc near *desc)
626 {
627 ct_data near *tree = desc->dyn_tree;
628 ct_data near *stree = desc->static_tree;
629 int elems = desc->elems;
630 int n, m; /* iterate over heap elements */
631 int max_code = -1; /* largest code with non zero frequency */
632 int node = elems; /* next internal node of the tree */
633
634 /* Construct the initial heap, with least frequent element in
635 * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
636 * heap[0] is not used.
637 */
638 heap_len = 0, heap_max = HEAP_SIZE;
639
640 for (n = 0; n < elems; n++) {
641 if (tree[n].Freq != 0) {
642 heap[++heap_len] = max_code = n;
643 depth[n] = 0;
644 } else {
645 tree[n].Len = 0;
646 }
647 }
648
649 /* The pkzip format requires that at least one distance code exists,
650 * and that at least one bit should be sent even if there is only one
651 * possible code. So to avoid special checks later on we force at least
652 * two codes of non zero frequency.
653 */
654 while (heap_len < 2) {
655 int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0);
656 tree[new].Freq = 1;
657 depth[new] = 0;
658 opt_len--; if (stree) static_len -= stree[new].Len;
659 /* new is 0 or 1 so it does not have extra bits */
660 }
661 desc->max_code = max_code;
662
663 /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
664 * establish sub-heaps of increasing lengths:
665 */
666 for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n);
667
668 /* Construct the Huffman tree by repeatedly combining the least two
669 * frequent nodes.
670 */
671 do {
672 pqremove(tree, n); /* n = node of least frequency */
673 m = heap[SMALLEST]; /* m = node of next least frequency */
674
675 heap[--heap_max] = n; /* keep the nodes sorted by frequency */
676 heap[--heap_max] = m;
677
678 /* Create a new node father of n and m */
679 tree[node].Freq = tree[n].Freq + tree[m].Freq;
680 depth[node] = (uch) (MAX(depth[n], depth[m]) + 1);
681 tree[n].Dad = tree[m].Dad = (ush)node;
682 #ifdef DUMP_BL_TREE
683 if (tree == bl_tree) {
684 fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",
685 node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
686 }
687 #endif
688 /* and insert the new node in the heap */
689 heap[SMALLEST] = node++;
690 pqdownheap(tree, SMALLEST);
691
692 } while (heap_len >= 2);
693
694 heap[--heap_max] = heap[SMALLEST];
695
696 /* At this point, the fields freq and dad are set. We can now
697 * generate the bit lengths.
698 */
699 gen_bitlen((tree_desc near *)desc);
700
701 /* The field len is now set, we can generate the bit codes */
702 gen_codes ((ct_data near *)tree, max_code);
703 }
704
705 /* ===========================================================================
706 * Scan a literal or distance tree to determine the frequencies of the codes
707 * in the bit length tree. Updates opt_len to take into account the repeat
708 * counts. (The contribution of the bit length codes will be added later
709 * during the construction of bl_tree.)
710 * TREE is the tree to be scanned.
711 * MAX_CODE is its largest code of non zero frequency.
712 */
713 static void
714 scan_tree (ct_data near *tree, int max_code)
715 {
716 int n; /* iterates over all tree elements */
717 int prevlen = -1; /* last emitted length */
718 int curlen; /* length of current code */
719 int nextlen = tree[0].Len; /* length of next code */
720 int count = 0; /* repeat count of the current code */
721 int max_count = 7; /* max repeat count */
722 int min_count = 4; /* min repeat count */
723
724 if (nextlen == 0) max_count = 138, min_count = 3;
725 tree[max_code+1].Len = (ush)0xffff; /* guard */
726
727 for (n = 0; n <= max_code; n++) {
728 curlen = nextlen; nextlen = tree[n+1].Len;
729 if (++count < max_count && curlen == nextlen) {
730 continue;
731 } else if (count < min_count) {
732 bl_tree[curlen].Freq += count;
733 } else if (curlen != 0) {
734 if (curlen != prevlen) bl_tree[curlen].Freq++;
735 bl_tree[REP_3_6].Freq++;
736 } else if (count <= 10) {
737 bl_tree[REPZ_3_10].Freq++;
738 } else {
739 bl_tree[REPZ_11_138].Freq++;
740 }
741 count = 0; prevlen = curlen;
742 if (nextlen == 0) {
743 max_count = 138, min_count = 3;
744 } else if (curlen == nextlen) {
745 max_count = 6, min_count = 3;
746 } else {
747 max_count = 7, min_count = 4;
748 }
749 }
750 }
751
752 /* ===========================================================================
753 * Send a literal or distance tree in compressed form, using the codes in
754 * bl_tree.
755 * TREE is the tree to be scanned.
756 * MAX_CODE is its largest code of non zero frequency.
757 */
758 static void
759 send_tree (ct_data near *tree, int max_code)
760 {
761 int n; /* iterates over all tree elements */
762 int prevlen = -1; /* last emitted length */
763 int curlen; /* length of current code */
764 int nextlen = tree[0].Len; /* length of next code */
765 int count = 0; /* repeat count of the current code */
766 int max_count = 7; /* max repeat count */
767 int min_count = 4; /* min repeat count */
768
769 /* tree[max_code+1].Len = -1; */ /* guard already set */
770 if (nextlen == 0) max_count = 138, min_count = 3;
771
772 for (n = 0; n <= max_code; n++) {
773 curlen = nextlen; nextlen = tree[n+1].Len;
774 if (++count < max_count && curlen == nextlen) {
775 continue;
776 } else if (count < min_count) {
777 do { send_code(curlen, bl_tree); } while (--count != 0);
778
779 } else if (curlen != 0) {
780 if (curlen != prevlen) {
781 send_code(curlen, bl_tree); count--;
782 }
783 Assert(count >= 3 && count <= 6, " 3_6?");
784 send_code(REP_3_6, bl_tree); send_bits(count-3, 2);
785
786 } else if (count <= 10) {
787 send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3);
788
789 } else {
790 send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7);
791 }
792 count = 0; prevlen = curlen;
793 if (nextlen == 0) {
794 max_count = 138, min_count = 3;
795 } else if (curlen == nextlen) {
796 max_count = 6, min_count = 3;
797 } else {
798 max_count = 7, min_count = 4;
799 }
800 }
801 }
802
803 /* ===========================================================================
804 * Construct the Huffman tree for the bit lengths and return the index in
805 * bl_order of the last bit length code to send.
806 */
807 static int
808 build_bl_tree ()
809 {
810 int max_blindex; /* index of last bit length code of non zero freq */
811
812 /* Determine the bit length frequencies for literal and distance trees */
813 scan_tree((ct_data near *)dyn_ltree, l_desc.max_code);
814 scan_tree((ct_data near *)dyn_dtree, d_desc.max_code);
815
816 /* Build the bit length tree: */
817 build_tree((tree_desc near *)(&bl_desc));
818 /* opt_len now includes the length of the tree representations, except
819 * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
820 */
821
822 /* Determine the number of bit length codes to send. The pkzip format
823 * requires that at least 4 bit length codes be sent. (appnote.txt says
824 * 3 but the actual value used is 4.)
825 */
826 for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {
827 if (bl_tree[bl_order[max_blindex]].Len != 0) break;
828 }
829 /* Update opt_len to include the bit length tree and counts */
830 opt_len += 3*(max_blindex+1) + 5+5+4;
831 Tracev((stderr, "\ndyn trees: dyn %lu, stat %lu", opt_len, static_len));
832
833 return max_blindex;
834 }
835
836 /* ===========================================================================
837 * Send the header for a block using dynamic Huffman trees: the counts, the
838 * lengths of the bit length codes, the literal tree and the distance tree.
839 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
840 * LCODES, DCODES and BLCODES are the number of codes for each tree.
841 */
842 static void
843 send_all_trees (int lcodes, int dcodes, int blcodes)
844 {
845 int rank; /* index in bl_order */
846
847 Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");
848 Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,
849 "too many codes");
850 Tracev((stderr, "\nbl counts: "));
851 send_bits(lcodes-257, 5); /* not +255 as stated in appnote.txt */
852 send_bits(dcodes-1, 5);
853 send_bits(blcodes-4, 4); /* not -3 as stated in appnote.txt */
854 for (rank = 0; rank < blcodes; rank++) {
855 Tracev((stderr, "\nbl code %2d ", bl_order[rank]));
856 send_bits(bl_tree[bl_order[rank]].Len, 3);
857 }
858
859 send_tree((ct_data near *)dyn_ltree, lcodes-1); /* send the literal tree */
860
861 send_tree((ct_data near *)dyn_dtree, dcodes-1); /* send the distance tree */
862 }
863
864 /* ===========================================================================
865 * Determine the best encoding for the current block: dynamic trees, static
866 * trees or store, and output the encoded block to the zip file. This function
867 * returns the total compressed length for the file so far.
868 * BUF is the input block, or NULL if too old.
869 * STORED_LEN is BUF's length.
870 * PAD means pad output to byte boundary.
871 * EOF means this is the last block for a file.
872 */
873 off_t
874 flush_block (char *buf, ulg stored_len, int pad, int eof)
875 {
876 ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
877 int max_blindex; /* index of last bit length code of non zero freq */
878
879 flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */
880
881 /* Check if the file is ascii or binary */
882 if (*file_type == (ush)UNKNOWN) set_file_type();
883
884 /* Construct the literal and distance trees */
885 build_tree((tree_desc near *)(&l_desc));
886 Tracev((stderr, "\nlit data: dyn %lu, stat %lu", opt_len, static_len));
887
888 build_tree((tree_desc near *)(&d_desc));
889 Tracev((stderr, "\ndist data: dyn %lu, stat %lu", opt_len, static_len));
890 /* At this point, opt_len and static_len are the total bit lengths of
891 * the compressed block data, excluding the tree representations.
892 */
893
894 /* Build the bit length tree for the above two trees, and get the index
895 * in bl_order of the last bit length code to send.
896 */
897 max_blindex = build_bl_tree();
898
899 /* Determine the best encoding. Compute first the block length in bytes */
900 opt_lenb = (opt_len+3+7)>>3;
901 static_lenb = (static_len+3+7)>>3;
902 input_len += stored_len; /* for debugging only */
903
904 Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",
905 opt_lenb, opt_len, static_lenb, static_len, stored_len,
906 last_lit, last_dist));
907
908 if (static_lenb <= opt_lenb) opt_lenb = static_lenb;
909
910 /* If compression failed and this is the first and last block,
911 * and if we can seek through the zip file (to rewrite the local header),
912 * the whole file is transformed into a stored file:
913 */
914 #ifdef FORCE_METHOD
915 if (level == 1 && eof && compressed_len == 0L) { /* force stored file */
916 #else
917 if (stored_len <= opt_lenb && eof && compressed_len == 0L && seekable()) {
918 #endif
919 /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */
920 if (!buf)
921 gzip_error ("block vanished");
922
923 copy_block(buf, (unsigned)stored_len, 0); /* without header */
924 compressed_len = stored_len << 3;
925 *file_method = STORED;
926
927 #ifdef FORCE_METHOD
928 } else if (level == 2 && buf != (char*)0) { /* force stored block */
929 #else
930 } else if (stored_len+4 <= opt_lenb && buf != (char*)0) {
931 /* 4: two words for the lengths */
932 #endif
933 /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
934 * Otherwise we can't have processed more than WSIZE input bytes since
935 * the last block flush, because compression would have been
936 * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
937 * transform a block into a stored block.
938 */
939 send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
940 compressed_len = (compressed_len + 3 + 7) & ~7L;
941 compressed_len += (stored_len + 4) << 3;
942
943 copy_block(buf, (unsigned)stored_len, 1); /* with header */
944
945 #ifdef FORCE_METHOD
946 } else if (level == 3) { /* force static trees */
947 #else
948 } else if (static_lenb == opt_lenb) {
949 #endif
950 send_bits((STATIC_TREES<<1)+eof, 3);
951 compress_block((ct_data near *)static_ltree, (ct_data near *)static_dtree);
952 compressed_len += 3 + static_len;
953 } else {
954 send_bits((DYN_TREES<<1)+eof, 3);
955 send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);
956 compress_block((ct_data near *)dyn_ltree, (ct_data near *)dyn_dtree);
957 compressed_len += 3 + opt_len;
958 }
959 Assert (compressed_len == bits_sent, "bad compressed size");
960 init_block();
961
962 if (eof) {
963 Assert (input_len == bytes_in, "bad input size");
964 bi_windup();
965 compressed_len += 7; /* align on byte boundary */
966 } else if (pad && (compressed_len % 8) != 0) {
967 send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
968 compressed_len = (compressed_len + 3 + 7) & ~7L;
969 copy_block(buf, 0, 1); /* with header */
970 }
971
972 return compressed_len >> 3;
973 }
974
975 /* ===========================================================================
976 * Save the match info and tally the frequency counts. Return true if
977 * the current block must be flushed.
978 * DIST is the distance of matched string.
979 * LC is match length - MIN_MATCH or unmatched char (if DIST==0).
980 */
981 int
982 ct_tally (int dist, int lc)
983 {
984 l_buf[last_lit++] = (uch)lc;
985 if (dist == 0) {
986 /* lc is the unmatched char */
987 dyn_ltree[lc].Freq++;
988 } else {
989 /* Here, lc is the match length - MIN_MATCH */
990 dist--; /* dist = match distance - 1 */
991 Assert((ush)dist < (ush)MAX_DIST &&
992 (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&
993 (ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");
994
995 dyn_ltree[length_code[lc]+LITERALS+1].Freq++;
996 dyn_dtree[d_code(dist)].Freq++;
997
998 d_buf[last_dist++] = (ush)dist;
999 flags |= flag_bit;
1000 }
1001 flag_bit <<= 1;
1002
1003 /* Output the flags if they fill a byte: */
1004 if ((last_lit & 7) == 0) {
1005 flag_buf[last_flags++] = flags;
1006 flags = 0, flag_bit = 1;
1007 }
1008 /* Try to guess if it is profitable to stop the current block here */
1009 if (level > 2 && (last_lit & 0xfff) == 0) {
1010 /* Compute an upper bound for the compressed length */
1011 ulg out_length = (ulg)last_lit*8L;
1012 ulg in_length = (ulg)strstart-block_start;
1013 int dcode;
1014 for (dcode = 0; dcode < D_CODES; dcode++) {
1015 out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]);
1016 }
1017 out_length >>= 3;
1018 Trace((stderr,"\nlast_lit %u, last_dist %u, in %lu, out ~%lu(%lu%%) ",
1019 last_lit, last_dist, in_length, out_length,
1020 100L - out_length*100L/in_length));
1021 if (last_dist < last_lit/2 && out_length < in_length/2) return 1;
1022 }
1023 return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE);
1024 /* We avoid equality with LIT_BUFSIZE because of wraparound at 64K
1025 * on 16 bit machines and because stored blocks are restricted to
1026 * 64K-1 bytes.
1027 */
1028 }
1029
1030 /* ===========================================================================
1031 * Send the block data compressed using the given Huffman trees
1032 * LTREE is the literal tree, DTREE the distance tree.
1033 */
1034 static void
1035 compress_block (ct_data near *ltree, ct_data near *dtree)
1036 {
1037 unsigned dist; /* distance of matched string */
1038 int lc; /* match length or unmatched char (if dist == 0) */
1039 unsigned lx = 0; /* running index in l_buf */
1040 unsigned dx = 0; /* running index in d_buf */
1041 unsigned fx = 0; /* running index in flag_buf */
1042 uch flag = 0; /* current flags */
1043 unsigned code; /* the code to send */
1044 int extra; /* number of extra bits to send */
1045
1046 if (last_lit != 0) do {
1047 if ((lx & 7) == 0) flag = flag_buf[fx++];
1048 lc = l_buf[lx++];
1049 if ((flag & 1) == 0) {
1050 send_code(lc, ltree); /* send a literal byte */
1051 Tracecv(isgraph(lc), (stderr," '%c' ", lc));
1052 } else {
1053 /* Here, lc is the match length - MIN_MATCH */
1054 code = length_code[lc];
1055 send_code(code+LITERALS+1, ltree); /* send the length code */
1056 extra = extra_lbits[code];
1057 if (extra != 0) {
1058 lc -= base_length[code];
1059 send_bits(lc, extra); /* send the extra length bits */
1060 }
1061 dist = d_buf[dx++];
1062 /* Here, dist is the match distance - 1 */
1063 code = d_code(dist);
1064 Assert (code < D_CODES, "bad d_code");
1065
1066 send_code(code, dtree); /* send the distance code */
1067 extra = extra_dbits[code];
1068 if (extra != 0) {
1069 dist -= base_dist[code];
1070 send_bits(dist, extra); /* send the extra distance bits */
1071 }
1072 } /* literal or match pair ? */
1073 flag >>= 1;
1074 } while (lx < last_lit);
1075
1076 send_code(END_BLOCK, ltree);
1077 }
1078
1079 /* ===========================================================================
1080 * Set the file type to ASCII or BINARY, using a crude approximation:
1081 * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
1082 * IN assertion: the fields freq of dyn_ltree are set and the total of all
1083 * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
1084 */
1085 static void
1086 set_file_type ()
1087 {
1088 int n = 0;
1089 unsigned ascii_freq = 0;
1090 unsigned bin_freq = 0;
1091 while (n < 7) bin_freq += dyn_ltree[n++].Freq;
1092 while (n < 128) ascii_freq += dyn_ltree[n++].Freq;
1093 while (n < LITERALS) bin_freq += dyn_ltree[n++].Freq;
1094 *file_type = bin_freq > (ascii_freq >> 2) ? BINARY : ASCII;
1095 if (*file_type == BINARY && translate_eol) {
1096 warning ("-l used on binary file");
1097 }
1098 }